docs: def create_core(self, thing_name, config_file, region=None,
                      cert_dir=None, account_id=None,
                      policy_name='ggc-default-policy', profile_name=None):
          """
          Using the `thing_name` value, creates a Thing in AWS IoT, attaches and
          downloads new keys & certs to the certificate directory, then records
          the created information in the local config file for inclusion in the
          Greengrass Group as a Greengrass Core.
  
          :param thing_name: the name of the thing to create and use as a
              Greengrass Core
          :param config_file: config file used to track the Greengrass Core in the
              group
          :param region: the region in which to create the new core.
              [default: us-west-2]
          :param cert_dir: the directory in which to store the thing's keys and
              certs. If `None` then use the current directory.
          :param account_id: the account_id in which to create the new core.
              [default: None]
          :param policy_name: the name of the policy to associate with the device.
              [default: 'ggc-default-policy']
          :param profile_name: the name of the `awscli` profile to use.
              [default: None]
          """
          config = GroupConfigFile(config_file=config_file)
          if config.is_fresh() is False:
              raise ValueError(
                  "Config file already tracking previously created core or group"
              )
          if region is None:
              region = self._region
          if account_id is None:
              account_id = self._account_id
          keys_cert, thing = self.create_thing(thing_name, region, cert_dir)
  
          cert_arn = keys_cert['certificateArn']
          config['core'] = {
              'thing_arn': thing['thingArn'],
              'cert_arn': cert_arn,
              'cert_id': keys_cert['certificateId'],
              'thing_name': thing_name
          }
          logging.debug("create_core cfg:{0}".format(config))
          logging.info("Thing:'{0}' associated with cert:'{1}'".format(
              thing_name, cert_arn))
          core_policy = self.get_core_policy(
              core_name=thing_name, account_id=account_id, region=region)
          iot_client = _get_iot_session(region=region, profile_name=profile_name)
          self._create_attach_thing_policy(
              cert_arn, core_policy,
              iot_client=iot_client, policy_name=policy_name
          )
          misc = config['misc']
          misc['policy_name'] = policy_name
          config['misc'] = misc